1. Technical Field
This disclosure relates to mechanisms for manipulating sections of rod or pipe to form drill strings, in particular, to mechanisms for gripping and holding sections of rod transported in carousel-type racks.
2. Background
A type of drilling equipment known as a blast hole drill is widely used in surface mining and quarrying operations. This equipment is typically mobile, being mounted on a vehicle that travels on crawlers. The vehicle has a cab for operating personnel and a housing for the machinery that drives the unit. A long, pivoting mast is disposed horizontally when the unit is on the move, and is set upright for vertical drilling operations. The mast carries a number of individually stored rods or pipes arranged longitudinally therein. These rods are connected one at a time in a drill string as a hole is being drilled.
Blast hole equipment is used in surface mining and quarrying operations to drill holes of moderate depth. Explosives are lowered to the bottom of these holes and detonated to break up rock and other hard earth formations. This permits the excavation of the material disintegrated by the blast and allows expansion of the area being mined or quarried.
Carrousel-type rod loaders are generally used to accommodate both drill rods and drill collars. The carrousel rod loader typically has upper and lower indexing plates that are rigidly attached to a vertically disposed axle, which permits the two plates to rotate together as a unit. The plates have suitable openings for holding and positioning the drill rod.
In certain mining operations, it becomes advantageous to position the mast at an angle, up to 30 degrees, for example, to drill a hole at that angle. There is a problem, however, in connecting drill rods to an angular drill string. If the drilling operation were conducted on the vertical, the top section of rod would be suspended from a drill head and lowered to connect it at the end of the drill string that projects vertically upward from the hole. When drilling at an angle, a rod that is connected at its upper end to the drill head will not be suitably supported at its lower end to permit alignment with, and a threaded connection to, the drill string. Some means is typically required to grip and support the rod to be connected and aligned with the drive and the drill hole.
It is advantageous to have more drill rods in a carousel, but this implies that the rods are closer together and thus there is less room for a mechanism to grip and support a rod. Also, when the carousel is operated at an angle off the vertical, there is a greater tendency for the rods to sag and an increased risk that a rod will escape the gripping device as it is being indexed over the drill hole. What is needed is a system that will both adequately support sagging rods and also take up minimal room to allow for use with carousels holding multiple rods.
The reader should note that this disclosure is not limited to the handling of drill rods for blast-hole drilling, but is applicable to other types of drilling, such as for water wells or petroleum-producing wells, or the handling of tubular parts generally.